Telephone system



Nov. 2, 1943. l. MLN'AR TELEPHONE SYSTEM Filed Oct. 19, 1942 15 Sheets-Sheet 1 I` MOLNAR v 2,333,485

TELEPHONE SYSTEM Nov. 2, 1943.

` Filed OCt. 19, 1942 13 Sheets-Sheet 2 VOICE PAD CURRENT REPEATER 206 -20I 202 205 ToLLLINE CIRCUIT-200 AUTOMATIC swITCHING a TOLL swITCHBoARD 1 EQUIPMENT TANDEM EXCHANGE 30 REMOTE EXCHANGE SIGNAL 'li- QRETARD .ll- NW- INVENTOR.

IMRE MCLNAR BY'OMI/UOMAMM ATTORNEYS Nov. 2, 1943. l. MOLNAR 2,333,485

TELEPHONE SYS TEM Filed oct. 19, 1942 15 sheets-sheet 5 ATTORNEYS Nov. 2, 1943.

l. MOLNAR TELEPHONE SYSTEM Filed Oct. 19, 1942 13 Sheets-Sheet 4 ]To IDENnTY EQUIP.

TOLL LINE CIRCUIT 200 IDENTITY L5 {IY-WL* ATTORNEYS v Nov. 2, 1943.- MOLNAR 2,333,485V

TELEPHONE SYSTEM Filed oct. 19, 1942 13 sheets-sheet 5 v UPY TOLL LINE CIRCUIT 200 2| 522 l1-H5 /544 cse TROUBLE .TONE

lINVENTOR.l IMRE MoLNAR Y l B OMW'MIWM ATTORNEYS Filed oct. 19. 1942 1:5 sheets-snee; E`

.2 42m 60 To| FlRsT sELEcToR soo c5712 63ml f V essalLfEegL H66'- Nov. 2, 1943. y LMOLNAR n 2,333,485 Y TELEPHONE SYSTEM 612 su *c5 SWW I iwi-M To#,WNesos LINE cgr,

I lvom 608 610) R649 l C573; 65| ./IH 673 g wTHRu l s .sem gfsels E RoNT. Reso M 670 M620 Ysls ATTORNEYS Nov. 2, 1943. MoLNAR TELEPHONE SYSTEM Filed ot. 19, 1942 N. 6. R. M @lo o T M .2 3 M E I fl W 2 .j 7 l 8 7 8 nl?. 7. .NI 8 8f8 ML* W 8 8 R S. v o 9 5 l vm Mv/M aOo 8 8 EO R WM 0 L m w. u. 8 E m w s 8 8 Dum Dv 3 N. N 3% 8 O 8 6 .aS .C h- 7 u M J L 3 .I H. 8 1f mm m 4 5 78 IInn T 5 5.33 WT 8 8 B8 S d 8 1. Dn am.: w. Rn. o lo 8 8 .I. C C C Jv IMRE MOLNAR Wfmywm ATTORNEYS NOV. 2, 1943. 1 MQLNAR 2,333,485

' TELEPHONE SYSTEM Filed Oct. 19, 1942 13 Sheets-Sheet 9 l- 9|2 I I 932/1 l Si Gen.

sfsgm +""T9'o3 TOLL vsacem; sELEGroR soo P935 I v I I WGY 9441 f943' `r M954 AH/ 945 V955 4 94d -4- j(956 |20 RM. T 0mm R920 93 v-J,`=C9o4 19 3 `V926 Q 6- 905 i927 92efL INVENTOR.

IMRE MoLNAR ATTORNEYS @.w nu

'fw 'W6' cII74,

`IIzIs neef- P- Il?? Ruso' Q JSUPT I oIsTANT l I Exc-RANGE y A 40 I coMMoII 'START Ano I EvEI. f DISTRIBUTOR cIRcUIT IIoI oIss l TRUNK PosITIoN DISTRIBUTOR n oIRcUITL K I nos E LIIIo` I INVENTOR.

IMRE MoLNAR BYMM.M%L

Nov. 2, 1943. I. MOLNAR 2,333,485

TELEPHONE SYSTEM Filed Oct. 19, 1942l l 13 Shee'bSR-Shee' l1 FIG."

clon) K mwARo TRUNK cIRcUIT IIook Oum RING f Ilzsjzl Ruso f cIo72 *t CIV/2y cm3) j' 4| I woM ATTORNEYS NW2, 1943. -LMO/LNAR 2,333,485

TELEPHONE SYSTEM ATTORNEYS Nv.2,1943. 'L MLNAR 2,333,485*

TELEPHONE SYSTEM" y ATTORNEYS Patented Nov. 2, 1943 "'UNiTED STA're-s PATIENT ori-rice Imre Molnar,-.Chcago, Ill., assignor to Automatic. y t Electric Laboratories, Inc., ,a corporation of Delaware Application octoberis, 1942, serial No. 462,519

` 1o claims.- (ci. '17a-'2.7)

Thepresent invention relates to telephonesystems and more particularly toj automatic`- tandem switching systems utilizing operator yswitchboard 'equipment of the character of that disclosed in the U. S. patents of Thomas F; Crocker, No. 2,167,710, granted August 1,"`1939,'and'No. 2,230,053,grantedJanuary 2 8, 1941.

, VA telephone systemfof the' automaticvtandem switching' Vtype conventionally" com'prisesj two principal exchanges interconnected'by toll lines; each exchangeincluding an automatictoll switch train, operator switchboard vequipment and outgoing trunks extending to 'suboices.1n handling toll trafc in the lsystemthe'operator at the switchboard in one exchan'gerst routes a connection therefrom .via the f a'ssociated toll switch train and an idle' 'toll` line tothe toll' switch train inthe otherjexchange; the lastmentioned toll .switch trainis then selectively controlled to extend the connection to'the'operator switchboard in theother' exchange, or to complete the connectionto a subscriber-"substar tion inthe other exchange independently ofthe operator switchboard therein,v or to extend the connection over a trunk to the associatedlsuboffice independently of theoperator switchboard in the other exchange.`

It is an object of the present invention tovpro'- vide in a telephone system of the type noted an improved toll line vcircuit disposed in'onej exchange and responsive 'toja stop" send lsignal transmitted over the associated toll line from the toll switch train in the other exchange 'for arresting operation rof the register sender-"associated with the operator switchboard in theone exchange and then for initiating-.reoperatin ofthe last-mentioned register ,sender` Va", timedinterval Another object of the inventiqri isto provide in a telephone system a, trunk circuit interconnecting two operator switchboard's, which trunk circuit embodies an improved arrangement Y,forl

controlling supervision.between"y the 'two'LswitLchboards incident to 'a rering operation performed at one of the switcl'iboards. v

A further Object 0f the inventionsidfprovidi in a telephone `systenr1l ,a'linefselectingl switch' which embodies an' improved arrangement fcr performing both timed ringP `and 'timedrering cperationsfover any line accessible to. tl 1`el n e which has been selected thereby.

Selecting mechanism inccr'pcrated' in the 'switch tou,

having incorporated thereinthe features ofthe invention, as briefly outlined above; and Fig. 1li iIluStrate'S'ithe-mode of combining Figs. 2 to 13, inclusive;to'form auniedsystem.x' Description ofthe-apparatus incorporated in the :1 i y j system Referring now more particularly to Fig. 1' of the drawings; they telephone system there illustratedconpris'es a remote exchange`20, a tandem exchange 30 and-a distant exchangeli', the tandeme'xchange V3l? constituting a-tol1 switching center-'for the system. jEach ofthe exchanges mentioned 'isofthe automatic type'ea-ch serving a number Aof local subscriber substations, the

tandem exchange 30 serving a number'of local subscriber lsubstationsv including the subscriber substation indicated at A. The remote exchange 2i] and the' tandemY exchange Y3i) are interconnte-d'by a number Of'tdll'lines, inciuainethe toll'line 2M; andfthe tandem exchange Se and the ldistantfexchange 4o are interconnectedV by a number of trunk lines, including the trunk line H365. The remote exchange '2t comprises automatic switchingl and `toll 'switchboard equipment of any suitable` type indicated at 22e; .and the distant exchanged() comprises automatic switching/ equipment of ,any suitable type, not shown.'

Onefendof the 'toll line 20| 'terminates 4in the equipment'ZZt provided inthe remote exchange 20 andthe `other end of the toll line 2M terminates in atoll line circuit 200 provided inthe tandem 'exchange 311.r The toll linecircuity Zito isl provided with an incoming trunk 560 and also. with an'outgoing trunk '510, the outgoingtrunlr 571i terminating in' a toll rstselectortllilindividu'al thereto provided in the tandem exchangev 3 l i, 10neend ofthe trunk `line vtutti terminatesA injthe equipment, `not shown, provided. in' the distant exchange 40; 'whilelthe other, end 'offthe trunk line' i065 terminates in atrunk circuiti I lo. of any' suitable type'provi'ded in the tandem 'exchange 30, the trunk circuit |110 being provided with an incoming trunk 1000. Also the tandem exchange comprises a number of toll second selectors, including the toll second selector 800, and a number of toll connectors, including the toll connector |380. The toll second selector 800 is provided with an incoming trunk 810 a-ccessible to the toll rst selectors 500 etc., and has access tov the incoming trunks |060 etc. extending to the respective trunk circuits 1 |0 etc. The toll connector |300 is of any suitable type and is provided with an incoming trunk 1390 accessible to the toll first selectors 000 etc., and has access to certain of the subscriber lines, including the subscriber line |381 extending to the subscriber substation A. Also it is noted that the subscriber line |381 extending to the subscriber substation A is provided with.; a line circuit |382, of any suitable type, individual thereto. Further the tandem exchange'30 comprises a number of inward trunk circuits including the inward trunk circuit 1100. The inward trunk circuit. |100 is provided with an incoming. trunk |010 accessible to the toll second selectors 000 etc., and an outgoing trunk |110.

`Further the tandem exchange 30 is provided with toll switchboard equipment of. the character of that disclosed. in the Crocker patents mentioned, this equipment comprisingl a number of operator positions Vincluding. the iirst operator position |201. The iirst operator position 120| is provided with va group of switching links individual theretov which are adapted to be selectively connected to an associated cable |210 extending to the first operator position [201.

The group of switching links individual to the first operator position 120| comprises the switching link illustrated which includes a link nder switchV |200 and a toll selector switch |300. The link finder switch |200 has access to the outgoing trunks |110 etc. extending from the inward trunk circuitsv |100 etc.; while. the tollselector switch |300 has ,access u tothe outgoing trunks 550 etc. extending to the toll line circuits 200 etc. and also to the incoming trunks 130,0 etc. extending to the toll connectors |380 etc. In the tandem exchangeY 30- the groups of switching links provided at thevarious operator positions at the switchboard, together with the toll first selectors 600 etc., the toll second selecr tors 800 etc. and the toll connectors |380 etc., constitute a toll switchy train.l Also the tandem exchange 30 comprises a local switch train, not shown, which is utilizedfor the purpose of settingup local calls between the various subscriber substations A etc. therein. Also the toll switchboard equipment comprises a `common start and level distributor 1 10 1 associated with the various inward trunk circuits |100 etc. and a position distributor 11.05, which is associated with the common start and level distributor 1101 and utilized for the. purpose oai; assigning idle ones of the operator positions at the swtchboard in aV predetermined,v order. Individually associated with the first operator vposition 120| are a sending key set DK and a sender link SL-1. The sender link SL-l comprises a switch LF-1 havingaccess: to, a. cable, 128,0 extending to the first operator position |201 and to a number of cables 12.05 etc. extending to the various switching links individually associated with the rst operator position 1.20.1', the Cable. l286being iIl.- divid'ual to the switching link illustrated. Also the sender link SL-1 comprises a. switch SS-I having access to a number of digit register and tions.

control circuits |390 etc. which are common to the operator positions at the switchboard.

Preferably, each of the toll line circuits is identical to the toll line circuit 200 which comprises, as best shown in Figs. 2 to 5, inclusive, a repeating coil 202 terminating one end of the toll line 201, a repeating coil 300 terminating the trunks 560 and 510, and a voice current repeater 205 and a pad 1205 interposed between the repeatingfcoils 202 and 300, the voice current repeater 205 and the pad 205 being of any suitable types. Also the toll line circuit 200 comprises a relay group, including a signal relay R210, a switch relay R320, a digit relay R330, a shunt relay R340, a. pad relay R350, a seizure 'relay R360, two rering relays R310 and R410,

an identity relay R420, a cutoff relay R430, a line-relay R44.0,-four control relays R450, R460, R410 an'd R510, an order relay R520, a seizure relay R530, a busy relay R540 and a, supervisory relay` R550. Further the toll line circuit 200 comprises a retard coil 213,' an order lamp 1.502, an order key K503; and a control network connected and arranged in a manner more fully described hereinafter. Y

, Preferably, each of the toll first selectors is identical to the toll rst selector 000 which comprises, as best shown in Figs. 6 and 7, a switch mechanism |v of the Strowger type, including a wiper set provided with four wipers 10| to 104, inclusive, mounted for both vertical and rotary movements, and an associated semi-cylindrical ContactV bank` provided with ten vertically spaced-apartjevers of contact sets arranged in circumferentially spaced-apart relation. Also the 'switch mechanism 100 comprises a vertical magnet M105 for driving the wiper set step by step thevertical direction away from its normal. vertical position. a rotary magnet M020,

for driving the 4wiper set step by Step in the rotary direction away from its normal rotary position, and' a release magnet M106 for releasing 'the .wiper set and for causing it to be returned to its normal rotary and vertical posi- Associated `with the switch mechanism '|00 ,are three sets of switch springs S015, S516 and S611 which are actuated whenl the wiper set is moved in the vertical direction away from its normal vertical position, a set of switch springs S0181 which is actuated when the wiper set is moved in the vertical direction away from its normal vertical position adjacent certain specified levels. and three sets of switch springs S019, S10'lar1d S110 which are actuated when the wiper set is driven in the rotary direction eleven steps away frornj its Vnormal rotary position. Further the toll"'rst selector 600 comprises a repeating vcoil 60|; a relay group, including a switch-through .relay R630, a line relay R040, a hold relay R650, a vtransfer relay R600, a control relay R610, two supervisory relays R and R130. an answer relay'RM, a trunk test relay R150,` anda 'cut-through relay R100; and a control network' connected and arranged in a manner morefully described hereinafter.

Preferablmeach of the tool second selectors is identicalto, the toll second selector G00 which comprises,v as best shown inv Figs.' 8 to 10, inclusive, aswitch mechanism |010 of the Strowger type, including a wiper set provided withve wipers1`10|`1 to |015, inclusive, mounted for both vertical and rotary movements, and an associated semi-cylindrical 'contact bank provided with ten vertically 'spaced-apart levels of contact sets arranged in circumferentially"spaced-apart relafrom-its normal vertical-position;ajrotary magnet'M906 for driving the wiper set step by step in'therotary direction away'from its normal rotaryl position, and a release magnet Mi'for releasing the' wiper'set and for causing it to be returned'to its normal'rotary and Verticalpositimer-'Associated with the switch mechanism II0`3aretwo sets ofiswitch springs SSI'I and S820 Which/are actuated when the Wiper setis movedin the rvertical directioniaway from its normal Vertical position, two'sets of switchjsprings S82I and SSI I which are actuated when the wiper set is moved in the' vertical direction away from its normal'verticalposition adjacent certainspecied levels and a set .of switch springs S908`which is-actuated when the wiper set 'is drivenin the rotary 4direction away from its normal rotary position. Further" thef'toll Vsecond selector 800 comprises a repeating coil 830; a relay group, includingv a switchthrough relay R850, a line relay R860, a vhold relay R810, two 'transfer relays R880 and R920, four control 'relaysfR930, RSM, R950'and'RI020,"ahuntrelay R950,` a trunk test relay'RI030 and a cut-through relay RIMB; and a` control'network connected and arranged inv a manner more fully 'described hereinafter.

Preferably, each of the inward: trunk circuits is'identica1 Yto the v4inward trunk circuit H00 which' comprises, as best shown in Figfll', a'relay group, including a cutoifrela'y RI IZEl, a control relayR'l 30, Va seizurel rel'ayRI-Iii, av `ring relay RI |50 andasupervisory relay RI Itill; and acontrol network connected and arranged ina manner more fully described hereinafter. Preferably, the 'common YStartand level'dis* tributor circuit I I0 l indicated in Fig. l1, is identi'- cal to the corresponding circuit shoWnin'Figs. 6 and 1() of the'laterCrocker patent;while the positionV distributor -I 05, indicated in Fig'. 11,:is identical tothe corresponding distributor' shown infFig. 10 of the later 'Crocker patent. Also the equipment provided at the lirst` operator position |201', indicated inFig. 12,"is identicaly to the corresponding'equipment shown in'Figs. 11: to v1li, inclusive, of the later Crocker patent; the link inder switchl |205, indicated in vFig.'12, is identical to-the corresponding switch 'shown in Fig. '7 of thelater Crocker patent;` while' the toll selector switch'lllll, indicated in" Fig. 13, is identical to the corresponding switch shown in Fig. 8' of the later Crockerpatent; Y- Y J Preferably, the sending key set DK, Aindicated in Fig-13, is identical `to thecorrespondingkey set shown in'Fig. `16 of the earlier Crocker patent; while Vthe digit register and-controlcircuitv I300, indicated in Fig. u13isv identical vto the corresponding circuit showninFigs. 17 to 2l,jinclusive-, of the earlier Crocketpatent.n Finally, the sender link SL-I ,indicated-in Fig. `12?,is substantially identical to the corresponding link shown'in Figs. l and V16 of the earlier Crockerpatent. f More particularly, the senderlink SLI-I is slightly different from the corresponding sender link mentionedin that it comprises the additional control relays RI350 andRI-ilil which are utilized for a purpose more fully explained hereinafter.

,v In the link finder switchlZiilL the toll selector sWitchI300, the rst operator position IZSI, the sender link SL-I and the digit register and control circuit i390,v the portions of the equipment illustrated in Figs. 12 and 13 are vprovided with reference characters similar-` Ato.thereference characters provided in conjunction with the cor'- responding portions of the 'equipment disclosed in the Crocker patents mentioned; the reference characters mentioned differing only in the first two numerals and 'being identical in-regard to the last two numerals. A better understanding of the connection and arrangementv of Vthe telephone .system'will ybe facilitated from Aa consideration of the detailed operation of the various pieces of apparatus 'inl corporated therein incidentv to the extension of the various calls between the exchanges illustrated, aswill appear hereinafter. n

Calii fromv the` remoteexchange to thetdndem exchange Considering now the extension ofy a Acall from the remote exchange 2i) to the tandem exchange 3 0, the operator at the switch-board in the remote exchange 20 controls. the associated equipment 220 in order to cause the automatic switching apparatus thereinto seize an idleA one o f the toll lines, such, for example,`as the toll-line 20|, exf tending to the tandem exchange 30. vWhen the toll line 20| isthus seized, battery potential inthe remote exchange 20 is applied to fth'e'line conductors thereof and, accordingly,`by wayfo'f the winding 203 of the repeating coil 202r to Vthesirriplex conductor C2 lll. The application of battery potential to the simplex conductor CZ I4 completes an obvious circuit for energizing theY intermediate and lower windings of the signal relay RZIO in series andals'o a` circuit for energizing the intermediate winding of the signal relay R2 I 0 in series with the retardcoil 2&3, in View of the fact that ground potential in the toll line circuit 200 is applied at this time byrWay of the contacts M3, 4343 and 552 to the control conductor C2I5. In View of the fact that the upperA winding ofthe signal relay R2I0 is normally energized, polarizing Ythis relay, the signal relay R2! 0 is operated. Upon operating, the signal relay R2 l iA completes, at the contacts 2l i, anl obvious path for applying ground potential to thecontrol conductorCZlZ, thereby to completel a series circuit for energizing .the windings of the seizure relay R530 and the'pad relay R350 in the toll line circuit 200 and the `line relay R540 in the toll rst selector 600. The above-mentioned circuit extends 4 from the grounded control conductor CM2 by way of the contacts'ill and the winding of R530 to the resistors 305 and 301; from the resistor 301 by way of the winding of R350 and the contacts 325 to the winding 3010i the vrepeating coil 300 and from the resistor 3M by way .of the contacts 3271 to the Winding 304 of the repeating coil 300; from the resistor 304i vby way of the contacts 325 to the winding 3020i the repeating coil 300; from the windings 302 and 304 of the repeating coil 300 by way of the contacts 352i and 323, the line conductors Cli andY CM2 of the trunk 5'6'0, the contacts. iiand 534 and the windings 602 and Eii of 'the repeating coil Si!! to the resistors 600 and 60.1;l from the resistor M53 to the resistor 6 I0; from the resistor GQ? by way 4of the resistor 60S to the resistor M0; and from the resistor iii@ by way, of the winding of Rilli) to battery. At this point itis noted that the resistor S09 is included in .the aboye-traced multiple branch the circuitextending fromthe resistor 6&0 yto the lwind ing of the seizure relay R539 so that the winding ofthe pad relay-R550 is energized, as previously noted.V .When this seriescircujit is thus completed theseizure relay R530 and the pad relayR35ll in the toll line circuit 200 and the line relay R550 in the toll first selector 600 operate.

Upon operating, the pad relay R350 completes, atthe contacts 351, an obvious path for applying battery potential by way of the resistor 308 to the pad conductor C201 extending to the pad 206 for pad control purposes. Upon operating, the seizure relay R530 completes, at the contacts 531, an obvious circuit for energizing the Wind- .ing ofthe busy relay R500, thereby to cause the latter relay to operate. Uponoperating, the busy relay R540 completes, at the contacts 545, an obvious path for applying ground potential to the control conductor C503 of the trunk 500, thereby to mark the trunk 550 as busy to the Various toll selector switches 1300 etc. having access thereto: and completes, at the contacts 501, an obvious path for applying ground potential to the control conductor C513 of the trunk 5110 extending to the toll rst selector 000. Also the busy relay R540 completes, at the contacts 503, an obvious circuit for energizing the lower winding of the supervisory relay R550 `and completes, at the contacts 542, a circuit traced hereinafter for energizing the'upper winding of the supervisory relay R550. When both the upper and lower windings of the supervisory relay R550 are thus energized this relaydoes not operate as it is of the differential type. f i

In the toll first selector 000, upon operating, the'line relay R040 completes, at the contacts 041-, an obvious circuit, including the contacts 031, for energizing the winding of the hold relay R050, thereby to cause the latter relay to operate. Upon operating, the hold relay R050 completes, at the contacts 551, a multiple path for applying ground potential to the hold conductor C513 of the trunk 510. The previously mentioned circuit for energizing the upper winding of the supervisory relay R550 in the toll line circuit 200 extends from the grounded control conductor C513 of the trunk 510 by way of the contacts 123, the contacts 100 of the set of switch springs S101, the contacts 030, the control conductor C514 of the trunk 510, thecontacts 502 and the upper winding of R550 to battery. Also the application of ground potential to the control conductor C513 of the trunk 510 completes `an obvious circuit, including the set of switch springs S611, for energizing the lowe1` winding of the answer relay R100, thereby to cause the latter relay to operate shortly thereafter, the answer relay R100 being of the combination slow-to-operate andslow-torelease type. Upon operating, they answer relay R140 completes, at the contacts '141, an obvious circuit, including the contacts 051, for energizing the winding of the control relay R010, thereby to cause the latter relay to operate. Upon operating, the control relay R510 completes, at the contacts 513, a multiple holding circuit, including the contacts 051 and 153, for energizing the lower winding of the answer relay R140. At this time the toll iirst selector 000 is prepared to be operated in response to a digit repeated thereto by the toll line circuit 200, in a manner more fully explained hereinafter.

The operator at the switchboard in the remote exchange then controls the associated equipment in order t-o cause the rst digit to be transmitted over the toll line 201', battery potential being removed intermittently from the line conductors thereof and consequently from the simplex conductor C214, whereby the signal relay R210 follows the impulses of the digit mentioned.

Each time the signal relay R210 restores and reoperates it interrupts and then recompletes the previously mentioned path for applying ground potential to the .control conductor C212, whereby the series circuit for energizing vthe windings of the seizure relay R530 and the pad relay R350 in the toll line circuit 200 and the line relay R640 in the toll rst selector 600 is controlled in order to cause the relays mentioned to follow the impulses of the first digit. The intermittent operation of the pad relay R350 and the seizure relay R530 in the toll line circuit 200 is without effect; While the intermittent operation of the line relay R640 in the toll first selector 600 effects operation thereof, in a manner more fully described hereinafter.

The operator at the switchboard in the remote exchange 20 controls the associated equipment, whereby several digits are transmitted over'the toll line 201 and repeated by the toll line circuit 200 over the trunk 510 by the signal relay R210', in the manner described above; the rst digit repeated over the trunk 510 operates the toll rst selector 600, as previously noted, and the subsequent digit or digits repeated over the trunk 510 operate the succeeding elements of the toll switch train, in a manner more fully explained hereinafter. After the connection has been extended via the toll switch train and when the call is answered, the toll rst selector 600 operates in order to cause ground potential to be removed from the control conductor C514 yof the trunk 510, thereby to interrupt the previously traced circuit for energizing the upper winding of the supervisory relay R550, whereupon the latter relay operates. Upon operating, the supervisory relay R550 interrupts, at the contacts 552, the previously traced path for applying ground potential to the control conductor C2 I5; and completes, at the contacts 551, lan obvious path, including the resist-or 310, for` applying battery potential thereto. The application of battery potential to the control conductor C215 completes an obvious alternative circuit, including the retard coil 213, for energizing the lower winding of the signal relay R210 andan obvious path, including the retard coil 213, forfshort-circuiting the intermediateA windingV of the signal relay R210, whereby battery potential is applied to the simplex conductor C214. When both the upper and the lower windings of the signal relay'R2111 are thus energized the latter relay remains in its operated position; however, the application of battery potential to the simplex conductor C214 and consequently to the line conductors of the toll line201 operates the equipment 220 to render answer supervisionto the operator at the toll switchboard in the remote exchange 20. At this time a connection is established from the toll switchboard in the remote exchange 20 Via the toll line 201, the toll'line circuit 200, the trunk 510, the toll rst selector 600 and the succeeding elements of the toll switch train to the called destination.

Considering now the release of the established connection from the remote exchange 20 to the tandem exchange 2.0, in the event the release is first initiated at the called destination, the toll first selector 600 is controlled in order to cause ground potential to be reapplied to the control conductor C514 of the trunk 510, thereby to recomplete the previously traced circuit for energizing the upper winding of the supervisory relay R550 in order to cause the latter relay to restore. Upon restoring, the supervisory relay R550 interrupts, at the contacts 551', the previously traced path for applying battery potential v to the control conductor C215, andcom'pletes, at the contacts 552, the previously traced path 'for applying ground potential to the control conductor C215. When batteryY potential is removed from the controlV conductorI C215 the previouslyl traced path for short-circuiting the intermediate winding of the signal vrelay R2I0`is interrupted; and when ground potential is -reapplied to t-hecontrol conductor C215 the previously *traced circuits -for energizing the intermediate fandlower windings of the signal relay R210 are rec'on'iplet'ecl, whereby the signal relay 'R210 remains'in Cits operated position. However, the removal of battery-'poten` tial from and the reapplicationhoffground potential to the control conductor'- -C215cause battery potential to -be'remoyed frorn'l'andfground potential to be reapplied to the simplex-conductorCZ I 4 and consequently to the line conductors of the toll line whereby the equipment 220 is operate'd-tolrender release superw'sion to the operator at the toll switchboard in the remote exchange 20. A'Ihevoperator atthe toll switchboard in the remote exchange 20 controls thefassociated equipment 220, whereby the automaticvswitching equipment releases the-toll line 20`1-fremovingbattery potential from the line Acon'oluctorsthereof and rendering'idle the toll Vline 20|. The removal of battery -potential in the equipment 220 in the remote exchange 20 fromthe toll kline 201 Yand consequently from-the simplexconductor. C2|4 interrupts the previously tracedy circuits for energizing the intermediate andlower windings of the signal relay R210, whereupon the latter Arelay restores.V Upon restoring,*thejsignaLrelay R210 interrupts, at the contacts 211,;'the previously mentioned path for-.applying ground potential to theY control conductor C212, thereby to interrupt the previously traced series circuit f or energizing the Vwindings of the seizure Arelay R530 and the pad relay 335e in the tourne circuit -200 and the line'relay R040 in the toll first selector 600 in the event the latter'relayocoupiesits operated position at this time, whereupon` thek relays mentioned restore. Upon Y rest orir 1g, the pad relay R350 interrupts, at'thecontacts 351,'the application of battery potential to the pad conductor C201, whereby the' pad 206'is controlled; Upon restoring,the seizure relay R530 interrupts, at the contacts A531, the previously mentioned circuit for energizing the winding ofthe busy 'relay R540, thereby to cause the latter `relaytfo` restore shortly tliereaitenv thetbusyirelayA R540 being, of the slowI-'to-release type. Uponf restoring, the busy relayRSli 'interrupt'sjfatftlie contacts A5115, the preyiouslyrmentioned path for applying ground ptntialto the control conductor C553` of the trunk 560, and.. completes, .at the contacts i5M, an obvious path, includingthec'oitats 521, for applying battery potential byway o; the winding of theY seizure relayv R360't6 ,the-control. conductor C563`of the trunk 560,- thereby to mark the trunk 1 560 asidle to thetoll selector switches`1300 etc.

Also-the busy relay;R5l10 interrupts, at the con` tactsl` 5t I, the previously mentioned path `f orgapplying vground potential tothe control conductor C513ofthe trunk- 5-'10 extending to fthe toll rst selectorfil. When ground vpotential is `removed from the controll conductorfC5'13 ofthe trunk 510 and the line relayirRSd-in the toll iirst selector 600is restored, the tollfrstfselector 600 `and the. succeedin'gf toll' `switch train are; released,.-in a manner. more `"fully explained hereinafter. ff Finelly theA busy relay R540 interrupts,` at the con-1r -ftacts 5542- and 511?,N theA previously"meritioned cuits for energizing the upper Aandlower,windings of the supervisory relay R550, whereby the latter Y the, to1-1prstfse1ector sco, wherebythe hue relay R040', the holdfrelay R650, the answer relay 'R145 'and the' vcontrol 'relay R610 *are operated, *all* in the manerlpreyiously explained: Also, as; preyiusly noted, "the YfirstV digit transmitted over-.the toll line 20| is repeated by the signal relay-R210 in the toll line circuit 200 to the'line relay/R040, v'v'he'rebyftheA latter relay follows the rdigit mentione'dz'v `'fConsidering' n'ow'the operation. ofr the toll firs *n selector t -600 in response' to j the control of fthejlinejrfrelayfRllU'in 'accordance with 'the first Fdigit, each time the line relay R540 Vrestores and*reeperateslitinterrupts' and then' recompletes, atfthe cont tsdthev previously traced circuit fo ener z ingthe winding oftheholdrelay R560 ho er; the latter relay remains'in vits operated position during impulsillg ,as it of the' slow-A tol-'release'jtype''Also' each'time the 'line relay R540 Irestores and.Y reoperates' 'it'U completesv and then interrupts, .at thecontacts:EiZ,V a multiple isruit, including the'uutautsst1653 andi 671s, for` energizing the` wir'idngV ofthe transfer relay R550@ and "for energizing ,Y t the" vvertical magnet M10 5 Awhereby the'l transferifr'elay 'R660' is' oper-Y at'ed' and ,remains operated during impulsing as itiis of `the"slgwftuereieasetype'and the vertical magnet Ml'opera'tes and4 restoresin order to drivethe wiper set oftheswitchjmechanism T00 onestepfinthevertical directinf Q L i l .1 Y l Uppn'operating the transfer'l relay R600 "completes; pat; the contacts 55 l ,t an`V obviousY path` for short-circuiting Yth" v ndingf'll of 'the ,repeating coill 60.1,V for alpuipo'se ,I orefully vexplained hr- 'Whel ,thel `i`15er Set j is ".dlven one" step iuuftr'A t 1 inthe vertical direction away from -itscriormal verticalpositiontnejsetsf switenspnugs sont, S6 |`6 flan AS10 [l are -actuatedf More particularly, weiser',ofswitcnspriugs .sa n is actuated into and,` shortly'l thereafter the :transfer relayilRE 60 n t 1 restoresc the'circuit:` forv energizing .the'iwinding vof the transferv relay R660 being interrupted,- at

the contacts 642, byV the operatedx line relay R640 at this time'. Upon restoring', the transfer relay R660 interrupts, at the contacts 66|, the;previ ously mentioned path. for Ashort-circuiting the windingv 603 of the repeatingcoil and completes, at the contacts 662, a circuit, including the contacts 15|, 165, the set of switch springs S615 and the contacts 62|, for` energizing the rotary'm'agnet M620. When thus energized the rotary magnet M620 operates, thereby to drive the wiper set one step the rotary direction away from its norrnal rotary position and to interrupt, at the contacts 62 the above-traced circuit for energizing the rotary magnet M620; rThe rotary magnet M620 then restores, thereby tore'- complete, at ythe contacts 62|, the previously traced circuitfo;- energizing the rotary nmagnet M620. Accordingly, the rotary magnet M620 opcrates intermittently, thereby to drive the wiper set step by step in the rotary direction vaway from its normal rotary position, whereby the trunks inthe lassociated level are successively tested. Y v

More particularly, when the wiper set engages a contact set in the associated level terminating a busy trunk, ground potential on the control conductor thereof is appliedto the control wiper 103, thereby to complete an obvious path, including the contacts 652, for short-ciruiting the 2 winding of the trunk test4 relay-R1r50. On the other hand, whenV the wi'perys'et engages a .contactv `set in the associated level terminating an idle trunk, battery potentialon the control concluctor thereof is. applied to the control wiper 103, thereby to complete an obvi'us circuit, including the contacts 652, for energizing the winding of the trunk test relay R150. When thus energized the trunk test relayv R150 operates to interrupt, at the contacts a point inthe previously traced circuit for energizing Atherotary magnet M620, thereby positively to prevent further operation of the latter in'ag'net and -to arrest further movement,v in the rotary direction'A of the wiper set.v Also Vthe trunktest relay R completes, at the vcontacts '152, an, obvious circuit,

Also the cut-through relay R160 completes, at

the'contacts 166,an"obvious path for applying ground potential to thefcontrol wiper 103 and an obvious multiple path for short-circuiting the winding `of `the trunk test relay R150 in order Ato cause the latter relay to restore.v Further the cut-through relay R completes, at-the con'-v tacts 100, an obvious path, including the con'- tacts 630 and 142, for applying ground potential to the control I`wiper 104 of the Wiper set; and interrupts, at the contacts 163, the previously traced holding circuit for energizing the lower winding of the answer relay R140. The answer relay R140 isv retained in its 'operated position at this time due to the completion 'of'the loop 'circuit for energizing the upper Yiiiindin'g thereof, this vcircuit extending from th'e line Wiper`10| by way of the contacts 16|, theicontacts 633, the winding 603 of the repeating Icoil 60'|,.the contacts 612 and 64|, the upper winding of.R140,.

Cil

the-windingll of the repeating coil 50| and the-contacts .636,- andv 162 to the line wiper 102. The abgve-described operation of the toll first selector 600,,takes-place when it is operated to select atrunk extending to an idle toll connector, such, forexarnplefasthe trunlrA |390, extending to tlieltollconnector |380. N-owassuming that the toll first-,selector 600 has operated'in the n iannerA described4` above and has selected the trunkw|380-extending,tothe toll connector |380,

the'toll first` selector 600'then receives two additional digits 1which are repeated thereby over the ti'unlr- ,|390gto the tollconnector |380. More'particularly; ithe line relay R640follows the second digit inj-order torepeat,' at the contacts 64|', the impulses thereof overathefpreviously traced loop circuit to the tolliconnector |380. Also the intermittent operation of the line relay R640 during the second, digit eiects reoperation of the transfer ,relay R660, whereby the latter relay recompletes, atfthe contacts 66|, the previously traced path for short-circuiting the winding 603 of the repeating coil '60| in order to improve impulsing over the loop circuit mentioned. It is noted that the answer relay R140 remains operated dring inipulsing as it is of the slow-torelease type. Further it is noted that each time the line relay R640 restores it `completes, at the contacts 642, aV circuit, including the contacts 631, 653, 615, 161 and 613, for energizing the lower Winding of the answer relayR140, thereby positively to prevent restoration of the last-mentionedrelay. At the conclusion of the second digit the line relay R640 remains operated, whereupon the transfer relay R660 restores shortly thereafter, in the manner previously explained, in order to interrupt, at the contacts 66|, the previously mentioned path for shortcircuiting the winding 603 Iof the repeating coil 60|, whereby the previously traced loop circuit, including lthe upper winding of the answer relay R140 andthe windings 603 and 605 of the repeating coil 60|, is again recompleted. In a similar manner, the line relay R640 `in the toll nrst selector 600 repeats the third digit over the trunk |390 to the toll connector |380.

The toll connectory |380 operates in response to the two digits repeated thereto by the toll rst selector 600 in accordance with conventional practice in order to select the corresponding subscriber line extendingV to a called subscriber substation. For example, the toll connector |330 may be operated to select the subscriber line 138| extending .to the called subscriber substation A. At this time the toll connector |380 tests the idle or busy condition of the subscriber line |38| extending to the called subscriber substation A.

In the event the subscriber line |38| extending to the called-subscriber substation A is tested as busy, the tbll-connector |380 may operate to 4cause busy 'tone current to be returned over the previously traced loop circuit, including the windings 603-'and 605 ofthe repeating coil 60|, whereby a corresponding busy tone voltage is induced in 'the windings v`60`25and"604 thereof in order to causebsy 'tone current to be returned over the trunk 510 to the windings 302 and-304 of the repeating coil 7300 iin" the `toll line circuit 200.v lThe busy tone current traversing the windings 302 and 304 of the repeating coil 300 causes busy tone current to be returned via the pad 206, .thevoice current 'repeater 205 and the repeating coil 202 'over 'the toll line 20| to the operator position :at the 'toll switchboard inv 'the remote exchange 20, in an obvious manner. Also the toll connector |380 operates in order to interrupt the previously traced loop circuit for energizing the upper winding of the answerrelay R140, whereby the latter relay restores shortly thereafter as it is of the combination slow-tooperate and slow-to-release type. Upon restoring, the answer relay R140 interrupts, at. the contacts 1x11, the previously traced circuit for energizing the winding of the control relay R610, thereby to cause the latter relay td restore shortly thereafter, the control relay R610 being ofthe slow-to-release type. Y

Similarly, in the event the subscriber Yline |30| extending to the called subscriber substation A is testedkas busy, the toll connector |380 may operate to cause ground potentialto beapplied intermittently to the negative line conductor of the trunk |350 and consequently tothe corresponding line wiper of the switch mechanism 100. kThis intermittent application of ground potential completes a circula-including the contacts 16| and 633, rthe winding 603 of the repeating coil 60| and the contacts 61|, for energizing in series the upper winding of the `supervisory relays R130 and R120. When this series circuit is completed the supervisory relay R130 operates to complete, at the contacts v132, an obvious holding circuit, including the contacts 65|, for-energizing the lower winding thereof.l On the other hand, the upper winding of the supervisory relay R120 is energized intermittently in; order to cause this relay to operate and restore.` Each-time the supervisory relay R120 operates and restores it interrupts and then recompletes, at the contacts 123, the previously traced path for applying ground potential to the control conductor C6113 of the trunk 510, thereby to cause the supervisory relay R550 in the toll line circuit 200 to operate and restore intermittently in order to render busy supervision to the operator at the toll switchboard in the remote exchange 20,in the manner previously explained.` l

On the other hand, inthe event the subscriber line-BBI extending to the called. subscriber substation A is tested as idle, the-toll connector |380 switches through in.L order-to interruptthe previously traced loop circuit Vfor energizing Athe upper winding -of the answer relay R140 in order to cause therlatter -relayto restore shortly thereaiterand elect the subsequent restoration of the control relay R610, in the manner previously explained,- 'Also the answer relayiR140 Hinterruptsjat the lcontacts 142, the previously traced path -for applying ground potential tothe control wiper'10fi ofthe wiper set.` Upon restoring, the control relay R610 recompletes, at the contacts 616, an alternative path, including the contacts 630 and 169,"ior reapplying ground potential to the control wiper 166 of the wiper set. Accordingly, ground potential is removed from and then'reapplied, a `short time interval later, to the control 4wiper 104. `The removal oi ground potential, during the vtime interval mentioned, from the control wiperv 104, causes the toll connector |386 to initiate a ringing operation, whereby ringing current is projected over the subscriber line ||v to the called subscriber substayWhen the subscriber at the called subscriber substationAjanswers the call a circuit iscom pleted for-,energizing in'series-the upper andV lower windings of the supervisory relay R120 andthe upper winding of the supervisory relay hlsfthis ireritlextendins from ground by' Waff ofthe lower/Winding of R120, the rcontacts 614,' the winding 605 of the repeating coil, 60|, the

, contacts v636 and 162 to the line wiper 102, and

from battery by way of the upper windings of the Asupervisoryrelays R126 and R130,.the,contacts l61|the winding 603 ofthe repeating coil and..the.contacts633 and 61| to the line wiper 10|; this loop circuit being extended by way ofthe trunk |390, the toll connector |380 andthe subscriber. line |381 .tothe .called subscriben substation A, whereat it is completed. Whenthe supervisory relays R120 and R130` are thus energized they operate. Upon operating, the supervisory relay R120 completes, at the contacts 122, an yobvious circuit, including the contacts for energizing the lower windingvof the supervisory relay. R130, and interrupts, at-the contacts 123, the previously traced path for applyingground potentialtothe control conductor C514 of the trunk 510 in order to interrupt'the previously traced circuit forV energizing theY upper winding ofthesupervisory relay R560in .the toll line circuit 200, whereupon the latterrrelay restores in the rmanner previously explained.

1 Alsothe supervisory relay R1,20,interrupts,at the contactsL 12|, a normally completed path, including -the. condenser 612 and theresistor 6| I across theline conductors (151| and C512 ofv the trunk 510, therebyto improve the delity ofr the repeating coiltlll. Upon operatingthe supervisory relayR130 completes, at the contaots13 2, an 0bvious, alternative holdingcircuit, including the contactsl, for4 energizing. ,the lower winding thereof. Also the supervisory relay lrlS-lllcompletes, atthe contacts 13|, an obvious path` for short-,circuiting lthe v uppervv winding thereof, thereby to reduce the `resistanl ofthe previously traced loop circuit extending. betweenfthe toll first selector 600 and the toll kconnector |300. At this time, transmission battery is appliedby way of the upper and lower windingsA of the supervisory relay R in the toll first selector 600viavthe ktrunk |390, thetollfconnector |380 and Ythe subscriber line |335 to the called, subscriber substation A.. l

A When the-subscriber, at the called subscriber substation A initiates the release of the established Yconnection by replacing the receiver of the telephone instrument thereat upony its yassociated s witchhook the previously traced loopcircuit for energizing in series the upperl and lower v windings of the supervisory relay R120 is interrupted, thereby t0 cause the latter relay to re-l Upon restoring, the supervisory relay y store. R120frecompletes, at the` contacts 113, the/previously--traced path for` applying ground potential tothe control conductor C514 of the trunk 510,*-thereby to recomplete the previously traced circuit for energizing the upper windingof .the supervisory relay R550 in the toll linecircuit 200 inv order tolfcause the latter relay to restore- I Upon restoring, the supervisory relay R550 causes release supervision torbe rendered to the operator at the toll switchboard in the remote exchange 20,'inthe manner.previously-explained.

'i The operator at the toll switchboard-inthe lremote exchange 20 then eiects the release of the automatic switching apparatus therein, whereby the toll line26| andthe toll line circuit 200 are released, in the manner previously explained, 

